SCIENCE HISTORY

In No Uncertain Terms
The Bohr family has finally released the mysterious letters that Niels Bohr wrote but never sent to Werner Heisenberg. They shed some light on the two physicists' mysterious meeting in 1941, which became the basis for Michael Frayn's play Copenhagen. In the letters, released in February, Bohr indicates that Heisenberg was not in fact stalling the Nazi atomic bomb program, as Heisenberg later claimed. "You spoke in a manner that could only give me the firm impression that, under your leadership, everything was being done in Germany to develop atomic weapons," Bohr wrote. The documents are not likely to be the last word, as some historians think Bohr could have misinterpreted Heisenberg's statements.

--Philip Yam